In learning or conversation, the Law of Primacy refers to the tendency for those learning or listening to recall information presented to them first more clearly, completely, and for longer durations.
When applied to persuasion, the Law of Primacy—or Primacy Effect, as it's sometimes called—holds that arguments presented first will tend to be more convincing than arguments presented thereafter.
In other words, if you want to win a debate, go first.
If you're able to establish your evidence before your opposition, the folks you're trying to convince will psychologically position your stance as their own, framing the next argument they hear as a deviation from the default they've subconsciously established.
That said, the Law of Primacy as applied to persuasion has been challenged: it was originally posited by in 1925, but in 1950 a concept called the Recency Effect was postulated and according to its tenets folks will better recall, and put more stock in arguments that were made last. So you'll be more likely to recall the last chapter in a book you just read, and you'll be more likely to agree with the last argument you just heard, because your brain has an easier time remembering that information clearly.
In the decades since the Law of Primacy and Recency Effect were proposed, more research has been done and it would seem that both effects apply at different times; sometimes we best recall the most recent information we've received and sometimes we cling to the first piece of information with which we're presented.
The degree to which primary or final data influences us may be determined by the amount of attention we're paying to the information, according to a theory posited in 1981; we latch on to different bits and then our attention decrements to the point where we bundle subsequent information under the header of the main piece of information we acquired when we were paying full attention; we store new information so that it's secondary to the main bit of information we registered fully.
Thus, if we're listening to an argument that largely agrees with our presuppositions, we might mentally document that information differently than we would an argument suggesting something completely distinct from our current conception of things. In some cases this will cause us to process this new information step-by-step because it's surprising and novel to us—which allows us to recall it more clearly, and we grant it more weight because of our bias toward information we can easily recall.
This is considered to be an important realm of inquiry because psychological biases and their influence on the relative persuasiveness of information is relevant to everything from court cases to political debates to proselytizing beliefs.
Also interesting in this case, though, is how muddled the whole concept has become as more research has been done.
At this point, at least, it's not clear that any particular presentation approach has a definitive advantage over any of the others: not in all contexts, at least. Which raises the question of whether these laws and effects are academic exercises rather than truly practical understandings.
It's arguably valuable for us to understand such things, but sometimes we reach a point in our exploration of a facet of human behavior where we come to the seeming conclusion that uncontrollable, internal variables—like what a person already believes or their preexisting propensity to vote—influence outcomes more than the effects we're testing.
Brain Lenses is an Understandary project.
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